The present invention relates to a valve, especially switch-over valves for large channel cross sections. The valve has a housing that is provided with channel connections, and a wing that is pivotably mounted in the housing by means of an articulation and that can be driven by at least one drive shaft and a fixation lever assembly that comprises a fixation lever secured to the drive shaft and at least one link rod that is pivotably connected on the one hand with the fixation lever and on the other hand with the wing.
Large wing switch-over valves are utilized to shut off channels in installation components, such as in desulfurization and nitrogen removal plants, and enable a continuing operation of the boiler via a bypass channel, even if the desulfurization and/or nitrogen removal unit must be shut down due to operating conditions.
Large wing switch-over valves are also used in gas turbine plants between gas turbines and waste heat boilers or exchangers.
EP 0 707 176 B1 discloses a fixation lever switch-over valve for large capacity cross sections, according to which, in the region of the channel connection for a bypass channel, there is provided a drive shaft that extends transversely through the channel. Connected with the shaft is a fixation lever assembly in order to pivot the wing. The internal fixation lever shaft is offset on the articulation shaft by about ⅙ of the nominal inside diameter of the bypass channel into the cross section of the bypass channel. The fixation lever shaft therefore produces an additional pressure loss. If a power plant is operated nearly entirely via the desulfurization and/or nitrogen removal unit, as is the case in Europe, the bypass channel is generally closed and the fixation lever shaft that is disposed in the bypass channel does not lead to an additionally generated pressure loss during normal operation. For the short period of bypass operation, this can be disregarded.
However, this evaluation is different if the power plants, for example as in the United States, are operated for half a year via the flue gas treatment unit, and in the other half year via the bypass. With such an arrangement, the fixation lever shaft that is disposed in the free channel cross section generates a pressure loss that must constantly be overcome, and which can no longer be economically disregarded, since in particular for channels having a large cross section an average loss of up to 15 to 20% can occur due to the drive shaft.
It is therefore an object of the present invention to improve a valve of the aforementioned general type such that the average loss due to the valve drive is reduced.